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Method and apparatus for controlling the concentration of a chemical solution

  • US 4,733,798 A
  • Filed: 02/05/1986
  • Issued: 03/29/1988
  • Est. Priority Date: 02/05/1986
  • Status: Expired due to Term
First Claim
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1. An apparatus for controlling the concentration of a detergent solution comprising:

  • (A) means for providing a concentration signal representing the concentration of the solution comprising a primary coil and a secondary coil, wherein when the coils are immersed in the solution the solution provides an electrical coupling between the coils;

    (B) means for changing the concentration of the solution; and

    (C) means for controlling the concentration changing means comprising;

    (1) means for comparing the concentration signal with a reference signal representing a preselected desired concentration and generating an error signal representing the difference therebetween; and

    (2) means for activitating the concentration changing means in response to the error signal, wherein the concentration changing means comprises means for increasing the concentration of the solution and wherein the activating means comprises;

    (a) timing means for;

    (i) continuously activating the concentration increasing means when the error signal indicates that the concentration of the solution is less than a preselected percentage of the desired concentration;

    (ii) not activating the concentration increasing means when the error signal indicates that the concentration of the solution is substantially equal to the desired concentration; and

    (iii) periodically activating the concentration increasing means when the error signal indicates that the concentration of the solution is between the desired concentration and the preselected percentage of the desired concentration, wherein the rate at which the concentration increasing means is activated is directly related to the difference between the actual concentration and the desired concentration, whereby overshoot is substantially eliminated; and

    (b) alarm means for determining whether the concentration increasing means has been continuously activated for an excessive period of time.

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